This size guide covers K2 FL3X Youth and Junior sizes in US, EU, and UK ski boot sizes.
Metric (cm) (inches below)
| SHELL LENGTH (mm) | MONDO POINT | US - MEN | US - WOMEN | EU | UK |
| 268 | 22.5 cm | 5.5 | 36 | 3.5 | |
| 277 | 23.5 cm | 6.5 | 37.5 | 4.5 | |
| 282 | 24.5 cm | 6.5 | 7.5 | 39 | 5.5 |
| 293 | 25.5 cm | 7.5 | 8.5 | 40 | 6.5 |
| 301 | 26.5 cm | 8.5 | 9.5 | 41.5 | 7.5 |
| 310 | 27.5 cm | 9.5 | 10.5 | 42.5 | 8.5 |
